He claimed descent from the de Gernon family, who are described as "
barons" in the
Domesday Book. His father Roger Gernoun was a military commander who distinguished himself during the
Bruce campaign in Ireland of 1315–1318. John also fought in the campaign and was wounded in the hand at the
Battle of Faughart in October 1318, where
Edward Bruce was killed.
The National Archives SC 8/82/4099
Petition of John Gernon of Ireland 1320 John was probably born in
Louth: he later owned land in
Dundalk. The Gernoun family had strong links to that county and gave their name to Gernonstown, an area with which John retained strong links, and where his descendants lived in the following century. Several members of the Gernoun family held the office of
High Sheriff of Louth between the fourteenth and seventeenth centuries. Richard Gernon, High Sheriff of County Louth, was
murdered in 1311, a casualty of a long-running
feud between the Gernouns and the prominent Brisbon family of
Dundalk. It is not clear if the judge was related to the wealthy English landowner John Gernoun, who died in 1384. ==Early career ==